Fluidic oscillator

ABSTRACT

A fluidic oscillator including a bistable element, and two control inlets, one being connected to atmospheric pressure, a feedback path from a first power outlet of the bistable element to the other control inlet, said feedback path including resistive means, a fluidic chamber capacitive means in series with a isolating flexible diaphragm device whereby a sustained oscillatory output is obtained at the second power outlet of the bistable element due to its continuous switching between its two states.

United States Patent Lapinas et al.

[451 Aug. 8, 1972 22 Filed:

[54] FLUIDIC OSCILLATOR [72] Inventors: Zigmas J. Lapinas, 594, 84th Ave. I

Laval, Chomedy, Quebec; Moses See Sum Wong, Apt. 202, 300

Joliette Street, Longueil, Quebec,

both of Canada July 13, 1970 [21] Appl. No.: 54,297

52 vs. C: ..137/a1,.s 511 1m. (:1. ..F15e 1/08 [58] Field 61 ..l37/8l.5

[56] References Cited UNITED STATES PATENTS 3,185,166 5/1965 Horton et al. ..137/s1.5 3,421,173 1/1969 Jones, Jr. ..137/s1.5 x

3,429,324 1 2/1969 Brown et al. ..l37/8l.5 3,403,691 10/1968 Hayes et al. 137/815 3,490,408 1/1970 Monge et a1 ..137/8l.5 X

Primary Examiner-William H. Cline Attorney-Nolte and Nolte 57 ABSTRACT A" fluidic oscillator including a bistable element, and two control inlets, one being connected to atmospheric pressure, a feedback path from a first power outlet of the bistable element to the other control inlet, said feedback path including resistive means, a fluidic chamber capacitive means in series with a isolating flexible diaphragm device whereby a sustained oscillatory output is obtained at the second power outlet of the bistable element due to its continuous switching between its two states.

SCIaImIDrawingHgure Pmmd Aug. 8, 1972 WMmW/M FLUIDIC OSCILLATOR This invention relates to fluidic devices and particularly to fluidic oscillator devices.

According to the present invention there is provided a fluidic element having a first state in which one out- ,put therefrom is provided at a first power outlet and a ing feedback means between the first power outlet andv a control inlet of said fluidic element whereby a control pressure is applied to said control inlet to at least switch sa1d fluidic element from one of said states to the other.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings in which:

The FIGURE is a diagrammatic representation of a fluidic oscillator device according to the present invention.

In the FIGURE the fluidic oscillator includes a bistable fluidic element 2 having a fluid stream power inlet 4, a first fluid stream power outlet 6 and a second fluid stream power outlet 8. The device also has a first control inlet port 10 which is open to the atmosphere and a second control inlet port 12, the bistable element being capable of assuming a first stable state or a second stable state under the control of the respective pressures applied to the control inlet ports. In its first stable state, the power fluid stream output is applied to the first power outlet 6 while in its second stable state the fluid output is provided at the second power outlet 8. It will be seen that the second power outlet 8 is connected on to the next stage which comprises the load of the oscillator, by way of fluid connection 14, and thus the output at the second power outlet 8 comprises the output of the oscillator device, i.e. it is the oscillator output.

The first power outlet 6 of the bistable element 2 is connected via a fluid connection 16 through a resistive means 18 a series with a capacitive means 20. The resistive means 18 is a flow. restrictor while the capacitive means 20 is a fluidic chamber having a predetermined volume. The feedback path between output 6 and control input 12 comprises resistive means 18, capacitive means 20 and diaphragm means 24 connected in series in that order.

As shown, the flexible diaphragm 22 is housed within the chamber of the diaphragm device 24 and it is so mounted that it isolates its one side from its other side. On the other side of the diaphragm 22 there is provided, in the diaphragm device 24, bias pressure inlet port 28 and bias pressure outlet port 30. The bias pressure outlet port 30 is connected, byway of a fluid connection Figure to the second control inlet port 12 of the bistable element 2, whereby a feedback means or loop is provided from the first outlet 6 of the bistable element 2 to the second control inlet 12 of the bistable element, by way of the fluid connection 16, the resistive means 18, the capacitive means 20, the fluid connection 26, the diaphragm device 24 and the fluid connection 32. The presence of the flexible diaphragm 22 results in an inherent infinite impedance, and the flexible diaphragm 22 is movable between a first position, indicated as "A" in the FIG. in which a bias pressure connection is made between the bias pressure inlet port 28 and the bias pressure outlet port 30 and a second position, identified in the Figure by B, in which the bias pressure connection between the said inlet and outlet ports is interrupted due to the movement of the diaphragm 22 into its second position.

The bias pressure applied to the bias pressure inlet port 28 is provided, by way of a connection 34, by a monostable vortex vent element 36, such as disclosed in United States Patent No. 3,403,691. A power fluid inlet is provided for the monostable element 36 from the main power fluid stream 38 by way of a fluid connection 40 which includes a trimming screw means 42 between thepower connection 38 and the power inlet port 44 of the monostable element. As shown, the inlet power fluid stream connection 38 is connected to the power inlet port 4 of the bistable element 2.

Operation of the device illustrated in the Figure is such that when an active and a passive switching of the bistable element is caused to occur in succession, due to the circuit arrangement, then an oscillator output is obtained from the second output outlet 8 of the bistable element and is thus applied to the oscillator load (not shown) connected to connection 14.

A constant bias pressure is applied by the monostable element 36 to the second control port 12 of bistable element 2 when the diaphragm 22 is in the position A. "The pressure thus applied to control port 12 actively switches the bistable element 2 so that the fluid stream output therefrom is switched from the second outlet 8. to the first outlet 6. Thus the fluid power stream output on connection 16 immediately starts charging up the capacitive volume in the capacitive means 20 through the resistive means 18 and, because of the isolation efl'ect resulting from the switching diaphragm 22, the rise time or time constant of the pressure on the feedback side of the diaphragm is determined solely by the RC combination of values of the resistive means 18 and the capacitive means 20.

The switching of the power fluid stream from the second outlet 8 to the first'outlet 6 by the positive pressure applied to control inlet port 12 may be referred to as active switching, and it will be observed that the normally active port of the monostable element 36 is connected, by connection 34, to the control inlet port 12 with the diaphragm in position A.

The passive switching of the power fluid stream output from the first outlet 6 to the second outlet 8 of the bistable element 2 now follows under control of the RC combination. If the bias pressure produced by the monostable element 36 is at a lower value than the recovery pressure of the bistable element 2 at the second control input port 12, then eventually the capacitive means 20 will be charged up to a pressure level at which the pressure applied by it to the one side of switching diaphragm 22 is such as to cause the diaphragm tobe deflected from position 'A to position B indicated by broken lines in the Figure. This deflection of the diaphragm 22 causes it to block the bias pressure outlet port 30 and to interrupt the bias pressure connection between the bias pressure inlet port 28 and the bias pressure outlet port 30. Thus the bias pressure is removed from the second control inlet port 12 and the blocking efiect of the diaphragm 22 on port 30 prevents entrainment of the power jet of the bistable element 2 on the second control inlet 12 causing passive switching of the power fluid stream from the first power outlet 6 to the second power outlet 8 of the bistable element 2. v

As soon as thefirst mentioned passive switching of the bistable element 2 has occurred, then the fluid power signal is removed from the first outlet 6 and the fluid, for'example, air, which has been stored in the For a low bias pressure setting, the reverse will also be true. The charge up time decreases while the discharge time increases and consequently a long N time with a short OFF time is obtained. In order to adjust the bias pressure, the trimming screw 42 is provided in the power supply path 40 of the monostable capacitive means 20 will start to discharge through the resistive means 18 to atmosphere through the bistable element 2: Eventually the pressure level in the capacitive means20 will decrease to a point'a't which it is overcomeby the bias pressure applied at the bias inlet port 28 by the normally active portof the monostable element 36. Thus the-diaphragm is deflected from position B back'to position A? and this simultaneously applies" the bias pressure to the second control inlet port .12 resulting in an active switching of the bistable element 2. The power fluid stream output therefrom is therefore switched from'the second-outlet 8 to the first outlet 6 of the bistable element 2.

As'will'be seen from the above description, active switching and'passive switching of the bistable element 2 occurs in succession and the oscillation sustains itself through the alternate applications of the passive and active switching 'modes, so as to provide an oscillatory output along connection 14 to the oscillator. load.

element 36. This trimmable adjustment is effective to trim the supply pressureand, sincethe recovery pressure (used as bias pressure) of the monostable element 36 is proportional to the supply pressure, then this trimming of the supply pressure will modify the bias level setting and alter the-ON OFF duty ratio of the Referring to the RC combination in the feedback line, it will be appreciated that to avoid a large volume for'the capacitive means 20, (where size is a limiting factor), the feedback resistive means 18 can theoretically be made infinitely high to provide the longest time constant required. Increasing the value of the resistive switching pressure difi'erential across the diaphragm at A 22. This means that the feedback circuit has a longer charging time. r a

When the passive switching modev occurs and a .power fluid stream output is fed through thesecond power stream outlet 8, then the output signal of the oscillator is ON and the capacitive means 20 begins discharging through the resistive means 18 as explained above. However, with the biaspressure set at a higher 1 level; as mentioned above, the capacitive means 20 requires a shorter time to decrease to that point at which the pressure on connection 26 is below the bias pressure applied to bias pressure inlet port 28 and at which the bias pressuretakes over and causesthe diaphragm 22 to move from position fB'to position A, resulting in an active switching mode of. the bistable element 2 whereupon the charging cycle again takes place since the power fluid stream output isnow applied to the first outlet 6 of the bistable element-2. With the additive efiect of longer charge time and shorter discharge time, the resultant frequency of the oscillator will have a long OFF time and a short ON time.

oscillator. 1

As will be appreciated, the oscillator frequency can be varied by changing the values of the extemalR and/or C feedback components, i.e. the resistive means 18 and the capacitive means 20;, In practice, typical frequency variation has been recorded from H:

down to 0.0016Hz (period 10 minutes) with the use of a single needle. valve (non-linear resistance device) and a small volume (1 cubic inch) in series. The vary long I time constant in the feedback line between output outlet port 6 and control inlet port 12 is made possible by the use of a very high resistance in conjunction with relatively small volume (capacitance) because of the .inherent infinite input impedance of the circuit. This infinite input impedance is derived from the flexible diaphragm 22 housed in its respective chamber of the diaphragm 24 so as to isolate the control inlet port 12 from the feedback connection line 26.'The deflection of the flexible diaphragm 22 (in response to the feedback signal) causes the active bistable ,element 2 to oscillate in a controllable mode. I

The incorporation into the oscillator of an adjustable duty ratio control is a particularly advantageous feature which allows an appreciable adjustment in the' ON OFF ratio (or mark space ratio) of the output frequency of the oscillator (from 1:2 to 2:1).

A practical oscillator was constructed which operated satisfactorily with air asthe operating fluid 'and it will be' appreciated that the oscillator will operate with most common gases and their mixtures and is thus not restricted to operation with air but may well operate with most fluids used in this art.

The illustrated bistable element has a special aerodynamic characteristic exhibited by a power jet whichentrains air from the control ports. This feature enables switching .to take place from the. first output outlet 6 to the second output outlet 8 by just blocking the second control inlet port 12 and leaving the first control inlet port l0 open to atmosphere (this is referred to herein as passive switching). The active switching, can also be accomplished by introducing a control pressure (10 to 15 percent of the power pres sure) 'to the control inlet port 12, thus switching the output fluid stream from the second output outlet 8 back to the first output outlet 6. The passive and active switching methods are employed in succession through the same control part to alternate the bistable output resulting in a sustained oscillation, as described above.

It would appear that the described embodiment of the invention, as constructed in a practical arrangement, includes certain advantages and features which are set forth below:

a. The oscillating phenomenon is effected by active and passive switching modes.

b. A flexible, barely moving thin diaphragm is employed to present an infinite impedance to the feedback input.

c. The frequency of oscillation is inversely proportional to the product of RC; thus the oscillator frequency can be varied over a range by means of a an adjustable needle valve or an adjustable volume. The former is usually more convenient. It would appear that stable oscillation can be achieved at very low frequencies with moderately small volume. i

d. Constant bias pressureis obtained from the active port of a monostable element through the use -of the vortex venting technique which automatically adjusts its flow to a varying load. This is particularly advantageous since at the point of blocking of the control inlet 12, the loading condition of the bias pressure port changes from a small load to an infinite or blocked load.

e. The ON-OFF duty ratio can be varied by a simple trimming adjustment.

f. The oscillator device comprises only 2 active elements and is simple in construction.

g. The output of the oscillator is compatible with the majority of loading conditions.

There has been described above an embodiment of a fluidic variable frequency oscillator which employs the principals of RC (resistance capacitance) feedback into an infinite impedance input; blocked control (passive) switching of a particular monostable element; and

the vortex vent used as a reference bias device. It will be appreciated that the invention is not restricted thereto and further modification and improvements will occur to those skilled in the art. For example, the bias pressure may be applied by any suitable device instead of by the monostable element 36.

We claim: I

l. A fluidic oscillator comprising:

a. a bistable element having a fluid stream power inlet, a first and a second power outlet, and a first and a second control inlet, the first control inlet being connected to atmospheric pressure,

b. a resistive means and a capacitive means connected in series between said first power outlet and one side of the diaphragm ofa diaphragm device,

0. said second power outlet being connectable to the oscillator load and comprising the output outlet of the oscillator, I

d. said diaphragm of the diaphragm device isolating said one side of the diaphragm from its other side,

e. said diaphragm device having a bias pressure inlet and a bias pressure outlet on said other side of the diaphragm, said bias pressure outlet being connected to said second control inlet,

f. said diaphragm being movable between a first position in which a bias pressure connection is made between said bias pressure inlet and said bias pressure outlet and a second position in which said bias pressure connection is interrupted,

g. a monostable vortex vent element connected to said bias pressure inlet to provide said bias pressure and having a fluid stream power inlet conoutput of the bistable element to be switched between saidfirst and second power outlets of the bistable element to produce an oscillatory-output at said output outlet.

2. A fluidic oscillator comprising:

a. a fluidic element having a first state in which one output therefrom is provided at a first power outlet and a second state in which an output is provided at a second power outlet,

b. a first control inlet of the fluidic element being connected to atmospheric pressure and a second control inlet being located on the opposite side of the fluidic element's power fluid stream opposite to saidfirst control inlet,

l c. switching means for switching said output between said first and second power outlets to provide an I oscillator output at said second power outlet including feedback means between the first power outlet and the second control inlet of said fluidic element whereby a control pressure is applied to said second control inlet to at least switch said fluidic element from one of said states to the other,

d. said feedback means comprising a feedback circuit including a resistive means in series with a capacitive means and a single stage diaphragm device having a flexible diaphragm in said feedback circuit between said control inlet and capacitive means,

'e. wherein when the output of said fluidic element is switched to said first power outlet, the capacitive means charges up until the positive pressure applied by it to one side of the diaphragm causes the diaphragm to deflect from a first position to a second position to cause the output of the fluidic element to switch from the first power outlet to the second power outlet,

-f. the capacitive means subsequently discharging through said resistive means to a point at which the pressure on said one side of the diaphragm is below the pressure on the other side of the diaphragm whereupon the diaphragm is deflected from its second position to its first position to remove said positive pressure at said second control inlet whereby said output of the fluidic element is switched from said second power outlet to said first power outlet due 'to the resultant entrainment at the first control input,

g. said diaphragm device being provided with a bias pressure inlet and a bias pressureoutlet on said other side of the diaphragm,

h. said bias pressure outlet being connected to said control inlet of the fluidic device,

i. a bias pressure being applied to said bias pressure inlet by bias-pressure means connected thereto, and

. j. said diaphragm in said first position permitting a bias pressure connection to exist between said bias pressure inlet and said bias pressure outlet and in said second position interrupting said bias pressure v connection. 3. A fluidic oscillator comprising:

. a. a fluidic element having a first state in which one output therefrom is provided at a first power outlet and a second state in which an output is provided at a second power outlet,

trol inletto at least switch said fluidic elementswitching means for switching said output between said first and second power outlets to provide an oscillator output at said second power outlet including feedback means between the first power outlet and a control inlet of said fluidic element whereby a control pressure is applied to saidconfrom one of said states to the other, a said feedback means comprising a feedback circuit including a resistive means in series with a capacitive means and a diaphragm device having a'flexi- 'ble diaphragm in said feedback circuit between said control inlet and said capacitive means,

. wherein when. the output of said fluidic element is through said resistive means to a point at which the pressure on said one side of the diaphragm is below the pressure on the other side of the diaphragm whereupon'the diaphragm is deflected from its second position to its first position and said output of the fluidicelement is switched from said second power outlet to said first power outlet,

said diaphragm device being provided with a bias pressure inlet and a bias pressure outlet on said the capacitive means subsequently discharging I I other side of the diaphragm. v g. said bias pressure outlet being connected to said control inlet of the fluidic device,

h. a biaspressure beingapplied to said bias pressure inlet, i. said diaphragm in said-first position permitting a bias pressure connection to, exist between said bias pressure inlet and said bias pressure outlet and in said second position interrupting said bias pressure connection,

j. said control inlet of said fluidic element being a second control inlet, the first control inlet being connected to atmospheric pressure and being located on the side of the fluidic element's power fluid stream opposite to said second control inlet,

k. including a monostable element having its nor-' mally active outlet port connected to the bias pressure inlet of the diaphragm device to provide said bias pressure. a

4. A fluidic oscillator according to claim 3 wherein an adjustment control means is provided in the power fluid stream input connection to said monostable element to permit adjustment of the bias pressure and thus the ON-OFF duty ratio of the oscillator output.

5. A fluidic oscillator according to claim 3 wherein a the resistive means is a flow restrictor and the capacitive means is a fluid chamber having a relatively small volume. 

1. A fluidic oscillator comprising: a. a bistable element having a fluid stream power inlet, a first and a second power outlet, and a first and a second control inlet, the first control inlet being connected to atmospheric pressure, b. a resistive means and a capacitive means connected in series between said first power outlet and one side of the diaphragm of a diaphragm device, c. said second power outlet being connectable to the oscillator load and comprising the output outlet of the oscillator, d. said diaphragm of the diaphragm device isolating said one side of the diaphragm from its other side, e. said diaphragm device having a bias pressure inlet and a bias pressure outlet on said other side of the diaphragm, said bias pressure outlet being connected to said second control inlet, f. said diaphragm being movable between a first position in which a bias pressure connection is made between said bias pressure inlet and said bias pressure outlet and a second position in which said bias pressure connection is interrupted, g. a monostable vortex vent element connected to said bias pressure inlet to provide said bias pressure and having a fluid stream power inlet connected to the power fluid stream connection of the power inlet of said bistable element, whereby an active switching and a passive switching of the bistable element occur in succession to cause the output of the bistable element to be switched between said first and second power outlets of the bistable element to produce an oscillatory output at said output outlet.
 2. A fluidic oscillator comprising: a. a fluidic element having a first state in which one output therefrom is provided at a first power outlet and a second state in which an output is provided at a second power outlet, b. a first control inlet of the fluidic element being connected to atmospheric pressure and a second control inlet being located on the opposite side of the fluidic element''s power fluid stream opposite to said first control inlet, c. switching means for switching said output between said first and second power outlets to provide an oscillator output at said second power outlet including feedback means between the first power outlet and the second control inlet of said fluidic element whereby a control pressure is applied to said second control inlet to at least switch said fluidic element from one of said states to the other, d. said feedback means comprising a feedback circuit including a resistive means in series with a capacitive means and a single stage diaphragm device having a flexible diaphragm in said feedback circuit between said control inlet and capacitive means, e. wherein when the output of said fluidic element is switched to said first power outlet, the capacitive means charges up until the positive pressure applied by it to one side of the diaphragm causes the diaphragm to deflect from a first position to a second position to cause the output of the fluidic element to switch from the first power outlet to the second power outlet, f. the capacitive means subsequently discharging through said resistive means to a point at which the pressure on said one side of the diaphragm is below the pressure on the other side of the diaphragm whereupon the diaphragm is deflected from its second position to its first position to remove said positive pressure at said second control inlet wheReby said output of the fluidic element is switched from said second power outlet to said first power outlet due to the resultant entrainment at the first control input, g. said diaphragm device being provided with a bias pressure inlet and a bias pressure outlet on said other side of the diaphragm, h. said bias pressure outlet being connected to said control inlet of the fluidic device, i. a bias pressure being applied to said bias pressure inlet by bias-pressure means connected thereto, and j. said diaphragm in said first position permitting a bias pressure connection to exist between said bias pressure inlet and said bias pressure outlet and in said second position interrupting said bias pressure connection.
 3. A fluidic oscillator comprising: a. a fluidic element having a first state in which one output therefrom is provided at a first power outlet and a second state in which an output is provided at a second power outlet, b. switching means for switching said output between said first and second power outlets to provide an oscillator output at said second power outlet including feedback means between the first power outlet and a control inlet of said fluidic element whereby a control pressure is applied to said control inlet to at least switch said fluidic element from one of said states to the other, c. said feedback means comprising a feedback circuit including a resistive means in series with a capacitive means and a diaphragm device having a flexible diaphragm in said feedback circuit between said control inlet and said capacitive means, d. wherein when the output of said fluidic element is switched to said first power outlet, the capacitive means charges up until the pressure applied by it to one side of the diaphragm causes the diaphragm to deflect from a first position to a second position to cause the output of the fluidic element to switch from the first power outlet to the second power outlet, e. the capacitive means subsequently discharging through said resistive means to a point at which the pressure on said one side of the diaphragm is below the pressure on the other side of the diaphragm whereupon the diaphragm is deflected from its second position to its first position and said output of the fluidic element is switched from said second power outlet to said first power outlet, f. said diaphragm device being provided with a bias pressure inlet and a bias pressure outlet on said other side of the diaphragm, g. said bias pressure outlet being connected to said control inlet of the fluidic device, h. a bias pressure being applied to said bias pressure inlet, i. said diaphragm in said first position permitting a bias pressure connection to exist between said bias pressure inlet and said bias pressure outlet and in said second position interrupting said bias pressure connection, j. said control inlet of said fluidic element being a second control inlet, the first control inlet being connected to atmospheric pressure and being located on the side of the fluidic element''s power fluid stream opposite to said second control inlet, and k. including a monostable element having its normally active outlet port connected to the bias pressure inlet of the diaphragm device to provide said bias pressure.
 4. A fluidic oscillator according to claim 3 wherein an adjustment control means is provided in the power fluid stream input connection to said monostable element to permit adjustment of the bias pressure and thus the ON-OFF duty ratio of the oscillator output.
 5. A fluidic oscillator according to claim 3 wherein the resistive means is a flow restrictor and the capacitive means is a fluid chamber having a relatively small volume. 